Conventional buck power supply systems sometimes use an analog comparator circuit to physically measure when the current in an inductor goes to zero so that a respective synchronous rectifier field effect transistor (e.g., low side switch connecting the inductor to ground) can be turned off. Turning off the synchronous switch at or around a time of measuring zero current in the inductor reduces and/or eliminates negative current in the inductor.
One way to measure current through the inductor is to physically measure a voltage indicative of a magnitude of current through the inductor via a comparator circuit. Since a magnitude of such a voltage sensed by the comparator can be quite small (e.g., such as in the millivolt range), a respective comparator in the conventional buck power supply typically has to be very precise and accurate.
In certain cases, the conventional comparator circuit for detecting a magnitude of current through the inductor must be co-located with a corresponding switch driver circuit to sense the voltage across the synchronous switch. When a switch driver and respective controller are separated from each other, the switch driver must transmit a communication signal back to the controller to notify the controller when the inductor current is negative and/or a time of turning off a synchronous rectifier switch. Based on receipt of the communication signal from the switch driver, the controller is able to switch between so-called discontinuous and continuous control mode operations.